Fuel filter system, especially for  diesel engines

ABSTRACT

The invention relates to a fuel filter system, especially for Diesel engines, comprising a filter housing ( 1 ) having a fuel inlet ( 27 ) and a fuel outlet ( 29 ) and a dehydrating filter medium ( 23 ) between the inlet and the outlet for the fuel to pass through, the filter housing ( 1 ) having a collection chamber ( 35 ) for the water trapped by the filter medium from which collection chamber the water can be supplied to a water absorbing and evaporating device ( 49 ) via a controlled dispenser ( 45 ), the components of the evaporating steam being releasable into the environment through the evaporating steam outlet ( 51 ) thereof. The fuel filter system is characterized in that the water absorbing and evaporating device ( 49 ) comprises a valve arrangement ( 59, 61 ) by means of which the evaporating water outlet ( 51 ) can be closed depending on an inadmissible amount of non-evaporated water ( 55 ) collected in the evaporating device ( 49 ).

The invention relates to a fuel filter system, especially for diesel engines, with a filter housing having a fuel inlet and a fuel outlet and a water separating filter medium through which fuel can flow and which is located between the inlet and outlet, the filter housing having a collection chamber for water that is separated by the filter medium; from said collection chamber water can be fed via a controllable release device to a water absorbing and evaporating device from whose evaporating outlet the components of the exhaust vapor can be released into the environment.

In order to protect the injection system, fuel filter systems are usually designed in such a way that not just impurities such as floating particulates, dust, etc., are separated, but also that water is separated and removed. Since the separated water may still be contaminated with diesel oil, it cannot be released directly into the environment. Specifically, the water may contain dissolved diesel components or micro-droplets that have not been separated by the pressure differential between the water and the diesel oil in the sump collected in the collection chamber. Consequently, it is prior art to provide measures for purifying the separated water before it is released into the environment.

In this context, a fuel filter system of the type mentioned above is known from EP 1 581 736 B1. This known solution specifies that separated water that is still loaded with substances that are harmful to the environment are not to be released into the environment directly in the fluid phase but rather are to be fed to an evaporation device from which the exhaust vapor is released into the environment downstream from the release device.

A generically different solution, cf. EP 1 726 818 A2, in which the separated water, without an evaporation or vaporization process taking place, is released into the environment in the fluid phase, specifies that, before release, there be a membrane that is permeable to water molecules, in the form of, for example, a ceramic membrane which retains the substances that are harmful to the environment. Aside from the fact that such membranes have to be replaced after a limited service life, they require that pressure be built up in order for flow pass-through to take place.

In view of the state of the art, the object of the invention is to provide a fuel filter system of the type mentioned above that is distinguished by greater operating reliability and particularly efficient purification.

According to the invention, this object is achieved by a fuel filter system having the features of claim 1 in its entirety.

In that, as specified in the characterizing part of claim 1, the water absorbing and evaporating device has a valve arrangement by means of which the exhaust vapor outlet of the evaporator device can be closed if an excess amount of unevaporated water collects in the evaporator device, it is possible to reliably avoid the risk that a malfunction of the system may pose a hazard to the environment. Even in the event of a failure of the control function of the release device, for example, in the case where a release valve remains permanently open or a release pump connected to the collection chamber remains continuously in operation, meaning that from the sump connected to the collection chamber an excessive amount of separated water still carrying pollutants and, potentially, diesel oil located even above the separation layer in the sump might reach the evaporator device, closing the exhaust vapor outlet prevents the environment from being polluted.

In advantageous embodiments, the water absorbing and evaporating device has an evaporator housing that can be connected to the collection chamber via the controllable release device; here the valve arrangement has a float valve that will close the exhaust vapor outlet if there is an excessive fill level of water accumulated in the evaporator housing. Such embodiments are distinguished by an especially simple and reliable construction. For example, the float valve can be designed as a ball valve in which a closing ball can be designed as a float which, when it floats upward, rests directly against a valve seat surface provided on the exhaust vapor outlet, closing it.

Here the arrangement can be advantageously designed in such a way that the filter housing defines a central vertical axis and that the evaporator housing is formed by a tube-shaped, central inner body of the filter housing, said inner body being coaxial with the axis. In the case of such a coaxial construction, the entire system, consisting of the fuel filter, water separator, collection chamber, and water absorbing and evaporating device, forms a single construction unit, for example, with an overall circular-cylindrical shape of a complete housing.

It is advantageous in this case for the outside of the inner body to be contiguous with the inner clean side of the concentrically arranged filter medium.

In an especially advantageous embodiment, the arrangement here is designed in such a way that the exhaust vapor outlet is placed upstream from the release device on the upper end of the inner body that forms the evaporator housing, so that exhaust vapor rising in the evaporator housing can exit from the overall housing directly from its upper end.

Since the boiling point of diesel oil far exceeds that of water, the exhaust vapor is virtually free of diesel oil if the boiling point is properly selected, for example, if it remains below the boiling point of water so that the exhaust vapor is essentially a rising water vapor or mist. The possibility cannot be ruled out, however, that even if the evaporation process is carried out properly, there may remain some residual pollutants in the exhaust vapor, for example, microparticles that are entrained by the vapor that is formed. With this in mind, in especially preferred embodiments, the arrangement is designed in such a way that an exhaust vapor filter device is provided upstream from the exhaust vapor outlet of the evaporator housing.

Since the exhaust vapor is pre-purified to be virtually free of diesel-oil components as much as possible because of the boiling process, an activated carbon filter device can be provided as an exhaust-vapor filter device. Since in the invention no separated water that still contains oil components is sent directly through the activated carbon filter because the filter is located downstream from the evaporator device, in which to a certain extent an aggregate change of state into the gaseous state takes place, the risk of saturation of the activated carbon and the associated loss of purification action is avoided.

In especially advantageous embodiments, the release of water from the release device can be controlled by a water sensor device that detects the water fill level in the collection chamber. In this way, the release processes can be structured in automatic operation in such a way that from the sump collected in the collection chamber in which gravitational separation (layering) between the diesel oil and water already takes place, the lower, heavier water portion is intermittently released in each case.

If the fuel pump of the correspondingly assigned internal combustion engine is arranged upstream from the fuel inlet of the filter housing, the release device can have a release valve that is controlled by the water sensor device. Conversely, if the fuel pump is connected to the fuel outlet of the filter housing, instead of the release valve there can be a pump that can be controlled by the water sensor device, said pump feeding the water to be released to the water absorbing and evaporating device against the underpressure that is generated by the fuel pump in the filter housing.

In order to allow the evaporation process to proceed in the desired way, so that a vaporization process occurs at a temperature that is preferably slightly below the boiling point of water, in advantageous embodiments in the evaporator housing there is a preferably controllable device for supplying heat, for example, in the form of a heating device or a heat exchanger for transferring heat from the cooling system, the lubricating system, or the exhaust gas system of an associated internal combustion engine.

Below the invention is detailed using embodiments which are depicted in the drawing. Here:

FIG. 1 shows a highly schematically simplified longitudinal section of an embodiment of the fuel filter system according to the invention, where during the operation of the system fluid media located therein are identified, and

FIG. 2 shows a longitudinal section, similar to that in FIG. 1, of a second embodiment of the fuel filter system according to the invention.

The invention is explained below using embodiments in which the fuel filter system is part of the system for supplying a diesel engine with diesel oil, not shown. It goes without saying that the invention can also be used in connection with other hydrocarbon compounds that serve as fuels in which it is desirable or necessary to separate water before combustion in the engine.

FIG. 1 shows a first embodiment with a filter housing, designated as a whole as 1, which is tightly sealed at the top by a removable cover 3. Aside from a bottom part 5, the housing 1 has an essentially circular-cylindrical shape with a central vertical axis 7. From the top of the housing 1, which is open when the cover 3 is removed, a coaxial inner body 9 is inserted into the housing 1, said inner body being sealed against the housing walls by means of sealing arrangements 11, 13, 15, and 17. With its coaxial inner pipe 19, the inner body 9 forms an evaporator housing, which will be detailed below.

The outer side of the inner pipe 19 abuts the clean side 21 of a concentric fuel filter device 23 that is mounted on the inner body 9 to whose dirty side 25 feed is directed via a fuel inlet, not shown, as indicated only by a flow arrow 27. After flowing through the filter device 23 from the outside inward, the diesel oil passes from the clean side 21 to a bottom-side fuel outlet 29.

The filter device 23 is built conventionally such that water separation takes place in a separation zone 31. As indicated by arrow 33, separated water together with diesel oil passes into a collection chamber 35, which is formed by a lower housing section that abuts the bottom part 5. Owing to the higher specific weight of water relative to diesel oil, during operation a bottom-side sump 37 consisting of the separated water forms in the collection chamber 35, where the upper separation line relative to the lighter diesel oil lying above it is designated as 39. The height of the separation line 39 of the sump 37 consisting of separated water relative to the diesel oil located above it is detected by a water level sensor 41.

As indicated by flow arrow 43, on the floor of the sump 37 a release device 45 is connected whose operation can be controlled based on the signals from the water level sensor 41. In the case of the embodiment, in which the fuel pump is arranged downstream from the fuel outlet 29 and where during operation an underpressure therefore prevails in the filter housing 1, the release device 45 has a pump 47. The operation of this pump is controlled by means of the water level sensor 41 in such a way that during operation enough water of the sump 23 is drained from the collection chamber 35 so that the separation line 39 does not drop to the connection point with the release device 45 such that the pump 47 delivers separated water to a water absorbing and evaporating device, which is designated as a whole as 49.

As part of the water absorbing and evaporating device 49, the inner pipe 19 of the inner body 9 forms an evaporator housing which upstream from the release device 45 extends coaxially upward to an exhaust vapor outlet 51 to which an exhaust vapor outlet 53 in the cover part 3 connects.

To ensure controlled evaporation of the water 55 that is delivered by the pump 47 into the evaporator housing 19, at the bottom of the evaporator housing there is an element 57 for the controlled delivery of heat. This can be a separate heating system or a heat exchanger for the delivery of engine heat, exhaust-gas heat, or coolant heat. Here it is particularly advantageous to use a PTC element, that is, a resistive element with a positive plot of the temperature coefficient, in which case regulating and control devices or overtemperature protection can be eliminated.

From the water 55 that is fed by the pump 47 and is pre-purified by gravity layer separation in the collection chamber 35, evaporation ensures the formation of a water mist or vapor which, as indicated in FIG. 1, rises in the inner pipe 19 and passes to the outside via the exhaust vapor outlet 51 of the inner pipe 19 and the vapor outlet 53 in the cover part 3.

As already mentioned, the water absorbing and evaporating device 49 contains a safety device in the form of a valve arrangement which closes based on the presence of an excessive quantity of unevaporated water 55 that has collected. In the case of the present embodiment, a float valve is provided for this purpose which as a closing body has a float ball 49 that works with a valve seat surface 61 on the exhaust vapor outlet 51 and which closes said outlet when it rises by making contact with the valve seat surface 61. When there is a normal quantity of fluid in the evaporator housing as controlled by the operation of the pump 47, the float ball 59, as shown in FIG. 1, is at some distance from the valve seat surface 61, the ball 59 resting on holding ribs 63.

The embodiment shown in FIG. 2 is distinguished from the embodiment described above by the fact that upstream from the evaporator housing 19 an exhaust vapor filter device, which is designated as a whole as 65, is connected to its exhaust outlet 51. This exhaust vapor filter device is located in the upper area of the inner body 9 which, with seal 67 inserted in between, is closed with a closed cover part 3, which has no exhaust vapor outlet 53. As the filter medium for the exhaust vapor filter device 65, an activated carbon filter 69 is provided which concentrically surrounds the end section 71 of the inner pipe 19. As indicated in FIG. 2, the water vapor or mist emerging from the end section 71 passes as a highly pure vapor or highly pure, condensed fluid from the top into the activated carbon filter 69 and leaves the housing via slit openings 73 that are made in the side wall surrounding the activated carbon 69.

Because of the pretreatment of the separated water 55 that is done by the evaporator device 49, other adsorptive materials besides activated carbon 69 can also be used; here, however, with most of the membranes and molecular sieves that can separate dissolved components, a differential pressure is required that can be built up by, for example, an auxiliary pump, such as is the case in the above-mentioned known solution that is foreign to the classification in question, according to EP 1 726 818 A2, or by having the water be superheated in the evaporator device in order to build up pressure. 

1. A fuel filter system, especially for diesel engines, with a filter housing (1) having a fuel inlet (27) and a fuel outlet (29) and a water separating filter medium (23) through which fuel can flow and which is located between the inlet and the outlet, where the filter housing (1) has a collection chamber (35) for water separated by the filter medium, from which collection chamber water can be fed via a controllable release device (45) to a water absorbing and evaporating device (49) from whose exhaust vapor outlet (51) the components of the exhaust vapor that is formed can be released into the environment, characterized in that the water absorbing and evaporating device (49) has a valve arrangement (59, 61) by means of which the exhaust vapor outlet (51) can be closed based on whether there is an excessive amount of unevaporated water (55) collected in the evaporator device (49).
 2. The fuel filter system according to claim 1, characterized in that the water absorbing and evaporating device (49) has an evaporator housing (19) that can be connected to the collection chamber (35) via the controllable release device (45) and that the valve arrangement has a float valve (59, 61) which closes the exhaust vapor outlet (51) based on an excessive fill level of water (55) collected in the evaporator housing (19).
 3. The fuel filter system according to claim 2, characterized in that the filter housing (1) defines a central vertical axis (7) and that the evaporator housing (19) is formed by a tube-shaped, central inner body (9) of the filter housing (1), said inner body being coaxial with the axis (7).
 4. The fuel filter system according to claim 3, characterized in that the outer side of the inner body (9) abuts the inner clean side (21) of the concentrically arranged filter medium (23).
 5. The fuel filter system according to claim 1, characterized in that the exhaust-vapor outlet (51) is located upstream from the release device (45) on the upper end of the inner body (9) that forms the evaporator housing (19).
 6. The fuel filter system according to claim 5, characterized in that an exhaust vapor filter device (65) is provided upstream from the exhaust vapor outlet (51) of the evaporator housing (19).
 7. The fuel filter system according to claim 6, characterized in that the exhaust vapor filter device (65) has an activated carbon filter (69).
 8. The fuel filter system according to claim 1, characterized in that the release device (45) can be controlled by a water sensor device (41) that detects the water fill level in the collection chamber (35).
 9. The fuel filter system according to claim 8, characterized in that the release device (45) has a release valve that can be controlled by the water sensor device (41) or a pump (47) that can be controlled by said sensor device.
 10. The fuel filter system according to claim 39, characterized in that a preferably controllable device (57) for supplying heat is present in the evaporator housing (19). 